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Abstract

A photodiode array spectrometer for determining the spectral composition of a plychromatic beam of radiation comprises diffraction means (10) which generate from the polychromatic beam a diffracted beam with a plurality of spatially separated diffracted rays of different wavelengths (.lambda..sub.1, .lambda..sub.2, .lambda..sub.3). A photodiode array (11) receives the diffracted beam whereby each photodiode intercepts a different spectral portion of the beam. A rotatable transparent plate (8) is provided in the beam path in front of the diffraction means (10) which, due to refraction of the beam upon entering and leaving the plate (8), permits to vary the direction of the beam impinging on the diffraction means (10) and therefore the direction of the diffracted beam in small steps depending on the angle of rotation of the plate (8). By the stepwise displacement of the diffracted beam across the photodiode array (11), a better sampling of the diffracted beam and therefore an improved spectral resolution is achieved. The invention can be used in the spectrometric analysis of a sample contained in a sample cell ( 5), whereby the sample cell is irradiated with polychromatic light from a light source (1).

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First Claim